Since composite materials constituted of an organic compound and a metal oxide can be expected to have mechanical, physical and chemical characteristics which are not owned by each of the materials, the development of such composite materials is keenly required in various fields. In particular, since composite materials composed of a polymer compound and a metal oxide have a mechanical characteristic combining toughness of the polymer and rigidity of the oxide, they are ranked as one of important materials of today. The composite materials composed of a polymer compound and a metal oxide are excellent in elasticity, abrasion resistance and chemical stability and are also expected as a tire or a shield material in the future. Furthermore, metal oxides containing an organic molecule are studied for applications over a wide range of from coloration of general-purpose materials to novel optical elements.
Now, the majority of characteristics of such composite materials become substantially valuable first time when fabricated in a thin film. For example, in the semiconductor industry of today, high integration of a layer of an electronic device is an important technical goal. But, in order to achieve this goal, a stable insulating thin film whose thickness is controlled at a nano level is absolutely essential. Also, in precision electronic instruments where mechanical friction is generated, such as hard disks, it is considered that a thin film having characteristics of adequate softness and abrasion resistance both of which conflict with each other at a glance is necessary.
As the thin film complying with these requirements, Patent Document 1 (PCT International Publication Pamphlet No. WO 03/095193) discloses a thin film constituted of a thin film layer of a polymer having a hydroxyl group or a carboxyl group on the surface thereof and a metal oxide thin film layer or an organic/metal oxide composite thin film layer which binds coordinately or covalently with the thin film layer of a polymer utilizing the hydroxyl group or carboxyl group and having a whole thickness of not more than 300 nm. This PCT International Publication Pamphlet No. WO 03/095193 also discloses a method for manufacturing such a thin film.
However, in the method described in PCT International Publication Pamphlet No. WO 03/095193, the organic layer and the inorganic layer are bound with each other by a coordinate bond or covalent bond of a carboxyl group or a hydroxyl group. For that reason, the organic layer and the inorganic layer are independent from each other, and when it is intended to keep strength and flexibility while making the film thin in thickness, there is generated a limit.
Now, in general, the more the surface area of a film is increased, the more a defect is easily generated on the film surface. For that reason, it is well known that there may be the case where a manufacturing method which can be applied in the case of manufacturing a film with a small surface area cannot be applied in the case of manufacturing a film with a large surface area. In particular, when it is intended to manufacture a film with a large surface area which is excellent in strength and flexibility, an additional problem tends to attend thereon.
Actually, an example for successfully manufacturing an ultra-thin film with a large surface area which is excellent in all of strength, durability and flexibility has not been known yet.
Patent Document 1: PCT International Publication Pamphlet No. WO 03/095193